1. Field of the Invention
The present invention relates to microwave combiners and more particularly to a continuous wave (CW) radio frequency (RF) combiner of the Wilkinson type that combines a number of inputs, e.g., 5 way, and is capable of very wide band and high power transmission.
2. Description of the Prior Art
Combiners are known in the microwave transmission art for combining a number of RF inputs into a single output in a transmission system. It is common in such systems to use combiners of the Wilkinson type, such as shown in FIG. 1, constituting output transformers, T1-T2, providing an output on terminal, J6, and a plurality of input transformers, e.g., five, T3-T7, receiving respective inputs on terminals J1-J5. The transformers are magnetically coupled through ferrite cores, FER1-FER7, and the transmissions are over coax cable transmission lines CC. A balancing resistor (R1-R4) is connected across each set of the input terminals, J1-J5, with a single resistor R5 connected across the extreme terminals J1 and J5. The value of the resistors is typically determined using the empirically evaluated characteristic impedance of the coax cables. The number of input transformers shown in FIG. 1 is five so that the combiner depicted is a 5 way combiner, but this type of combiner also may have other numbers of inputs applied thereto, particularly continuous wave (CW) inputs.
In such combiners, the operating frequency range and power is limited by the ferrite loaded input with an extended frequency range being dependent upon the selection of the proper ferrite material as well as the parasitic inductance and capacitance of the other components. The power level is a function of the resistor layout and the sizes of the ferrite and coax cables.
It is therefore a problem in the art to achieve an extended frequency range in CW Wilkinson type combiners with higher power operation.
It is accordingly an object of the present invention to provide an improved RF combiner with an extended frequency range and higher power operation.
It is another object of the invention to provide a CW Wilkinson type combiner capable of operating with a very broad band of frequencies and a high power level having large balancing resistors.
It is a further object of the invention to provide an improved CW RF combiner with an extended frequency range of 2 to 150 MHz and higher power operation at a minimum 4 KW power level.
It is also an object of the invention to provide an improved CW RF combiner with an extended frequency range and higher power operation and of an odd number of inputs to be combined.